1. Field of the Invention
The invention concerns a device for determining the delivery rate or the mass flow rate of a material conveyed through a delivery conduit by a high-density liquid piston pump comprising at least a conveyance cylinder and a conveyance piston. During a filling stroke (suction stroke) the conveyance cylinder is filled with a material from a material providing container, and during a pressure stroke, with displacement, the material is emptied into the delivery conduit.
2. Description of the Related Art
Principally with high-density pumps, which are incorporated into a process engineering or engineering chemistry process, there is a requirement to measure and document the mass flow rate and to use this measured value in certain cases as the control value or set value for plant units or equipment situated upstream or downstream or and to incorporate this in a feed back system. This is the case for example in the conveyance of sewage sludge for the incineration of sewage sludge.
Volumetric flow meters in the form of cams-counters for Newtonian fluids are known, which are built into the delivery conduit as "motor" and in which a volume wheel is caused to rotate as a consequence of the pumping process. The revolutions of the volume wheel are added via an impulse disk and converted into volumetric flow in an evaluation unit on the basis of the known displacement volume.
Further, it is known in the case of two-cylinder high-density fluid pumps, to derive the delivery flow rate of the high-density liquid pump having a defined displacement volume from the stroke count. In this measurement method, the amount of filling of the high-density liquid pump must be estimated. For this reason the result can strongly fluctuate on the basis of a changing consistency of the high-density fluid. In order to avoid this problem, it was proposed (DE-A-40 35 515) to determine the amount of filling of the cylinder during each stroke with the help of the most diverse indicators. This method has also been found to be too imprecise for many applications, since for the determination of the mass flow rate in interest it is necessary additionally to determine the density of the material, which causes great fluctuations depending upon the consistency of the high-density or thick stock.